| Abstract | The effect of epoxy chemistry, level of clay dispersion, and clay concentration on the fracture toughness of epoxy nanocomposites was studied. Three epoxy matrices with different glass transition temperatures (Tg) were chosen for this work. The epoxy resin EPON 828 cured with Jeffamine D-2000 is a rubbery material with a glass transition temperature Tg = -46.3°C, while the material prepared with Jeffamine D-230 is a glassy solid with a higher Tg of 86.8°C. A glassy solid with a yet higher glass transition temperature of Tg = 150.4°C was obtained upon curing with BF3·MEA via homopolymerization of epoxy and hydroxyl groups. The nanocomposites were prepared with the organoclay Cloisite 30B from Southern Clay Products. Fracture toughness properties of epoxies and epoxy nanocomposites were measured according to ASTM standards D5045-99. Fracture surfaces were analyzed by field emission gun scanning electron microscopy (FEGSEM). The quality of dispersion and intercalation/exfoliation were analyzed by X-ray diffraction (XRD). The results indicate that fracture toughness of the epoxy systems is enhanced with the addition of nanoclay, but the level of increase in fracture toughness depends very much on the clay dispersion, the clay concentration, and the nature of the epoxy. |
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